Micro capillary-force driven fluidic accumulator/pressure source

Future portable, continuously monitoring, ultra low-power fluidic bioassay systems are likely to require fluidic pumping devices allowing the actuation of fluids with a minimum expenditure of electrical energy. One method to accomplish this is to utilize a micro-osmotic pump coupled with a micro capillary-force driven fluidic accumulator to make possible a pressure source that requires no electrical power. This paper reports new micro structures to harness surface tension forces and thereby make possible micro fluidic accumulators in a planar wafer-level process, allowing for simple integration with other microfluidic devices such as pumps, valves, and mixers. Experimental results show that fluid can be stored at predictable and elevated pressures in this device after being charged by an external pressurized source (accumulation). The stored fluid can be dispensed later at a near constant pressure depending on the output fluidic resistance. Pressures of 6500 Pa and flow rates as high as 7.2 /spl mu/L/min with a dispensed volume of 1.2 /spl mu/L were achieved without electrical energy.